Method of forming concrete structures with etched-aluminum forms

ABSTRACT

A METHOD FOR FORMING A CONCRETE STRUCTURE IN A CONSTRUCTION FORM MADE OF ALUMINUM PANELS HAVING CONCRETECONTACTING SURFACES WHICH ARE TREATED TO REDUCE ADHERENCE TO THE CONCRETE. THE SURFACES OF THE PANELS ARE CONTACTED BY AN ETCHING AGENT TO REMOVE OXIDE FILM AND TO ROUGHEN THE SURFACES. AN OIL SUBSTANCE IS THEN APPLIED TO THE ETCHED SURFACES, AND CONCRETE IS POURED INTO THE ETCHED AND OILED FORMS TO PRODUCE THE DESIRED STRUCTURE. THE PANELS ARE STRIPPED FROM THE STRUCTURE WHEN THE CONCRETE HAS HARDENED.

J1me 1971 F. WILLIAMS METHOD OF FORMING CONCRETE STRUCTU RES WITH ETCHED-ALUMINUM FORMS Filed Aug. 14, 1969 United States Patent Ofice U.S. Cl. 264-31 1 Claim ABSTRACT OF THE DISCLOSURE A method for forming a concrete structure in a construction form made of aluminum panels having concretecontacting surfaces which are treated to reduce adherence to the concrete. The surfaces of the panels are contacted by an etching agent to remove oxide film and to roughen the surfaces. An oil substance is then applied to the etched surfaces, and concrete is poured into the etched and oiled forms to produce the desired structure. The panels are stripped from the structure when the concrete has hardened.

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of my copending application Ser. No. 426,885, filed Jan. 21, 1965, now U.S. Pat. No. 3,468,988.

BACKGROUND OF THE INVENTION The use of concrete-wall construction panels which are made of aluminum or aluminum alloys has become widespread in recent years. One disadvantage in aluminum construction panels is the tendency of them to stick to the concrete. This makes it rather difiicult to remove the panels from the hardened concrete. Certain types of the aluminum construction panels cause a simulated brick effect to be formed in the finished concrete wall. The sticking of the construction panels to these surfaces results in the panels pulling 01f fragments of the hardened concrete when they are removed therefrom. Ths results in a somewhat less than desirable decorative surface on the concrete wall due to the holes, etc. caused by the fragments being pulled from the concrete.

Building contractors have attempted to prevent the construction panels from sticking to the concrete by oiling the interior faces of the construction panels. The use of oil on aluminum construction panels has not solved the problem of sticking to concrete.

Therefore, it is a principal object of this invention to provide a concrete-wall construction panel which is chemically etched and then oiled to prevent it from sticking to the concrete. Another object of this invention is to provide a concrete-wall construction panel which may be removed from a concrete wall without removing fragments of the wall. It is a further object of this invention to provide a concrete-wall construction panel which is economical, durable, and practical to use.

SUMMARY OF THE INVENTION Briefly stated, this invention relates toa method for forming a concrete structure in an assembly of aluminum panels having inner aluminum surfaces defining a construction form. An etching agent is first applied to the inner surfaces of the panels, and an oil substance is next applied to the surfaces which have been etched and roughened by the etching agent. Concrete is then poured into 3,584,088 Patented June 8, 1971 the construction form defined by the inner surfaces, and allowed to harden into a formed structure. The etched and oiled panels are then stripped from the formed structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the concrete-wall construction panel;

FIG. 2 is a sectional view of the wall construction panel DESCRIPTION OF THE PREFERRED EMBODIMENTS The numeral 10 generally designates a construction panel having an interior face 11 (which is irregular to form a simulated-brick appearance on concrete), an exterior face 13, and edge flanges 15. As seen in FIG. 2, the numeral 17 represents face 11 after it has been chemically etched and roughened in preparation for application of an oil substance which prevents the panel from sticking to the concrete which is generally indicated at 19 in FIG. 3.

Etched face 17 is formed on panel 10 by either of the following examples:

Example No. 1.A quantity of caustic soda (sodium hydroxide) and a quantity of water are first heated. The heated water and caustic-soda etchant solution is then applied to panel 10 by any convenient method such as by dipping panel 10 into the heated solution or by spraying or brushing the solution onto panel 10. It is only necessary to treat the inner surface of panel 10 as it is only the inner surface thereof which comes into contact with the concrete. Panel 10 is then allowed to dry.

The surface of certain aluminum alloys may take on a black or soot-colored appearance after etching as just described. This coloration is called smut, and arises primarily from alloying elements in the aluminum such as copper or manganese which are not soluble in caustic soda. The formation of smut does not interfere with the use of the etched aluminum panels, and appears to provide somewhat improved release of the treated and oiled panels from concrete.

It has been discovered that a suitable proportion of caustic soda to water is approximately 5-10% by weight. While other proportions work with varying degrees of success, the foregoing range is the most desirable. It has also been found that the best results are obtained when the caustic soda-water solution is heated to -160 degrees Fahrenheit. Varying degrees of success are obtained in forming etched surface 17 by varying the solution temperature but the foregoing range has been found to be the most desirable.

Example No. 2.A quantity of muriatic (hydrochloric) acid is applied to panel 10 by any convenient means such as described in Example No. 1. The muriatic acid reacts with the aluminum and/or aluminum alloys in panel 10 to etch and roughen the treated panel surface, A soot-colored smut may be formed on the etched surface, but is typically not quite as black as the smut described in Example No. l. Desmutting treatment is not required in normal applications.

The normal method of subsequent operation is as follows: A plurality of panels 10 with etched and roughened surfaces 17 are assembled to provide a wall construction form such as seen in FIG. 3. Surfaces 17 are then coated with a layer or film of conventional concrete-form oil (such as sold under the trademarks Nox-Crete and Debond to aid in removing the panels from the hardened con- 3 crete. The concrete is poured into the form and permitted to harden in conventional fashion. When the concrete has hardened, panels 10 are stripped or removed therefrom. The form oil adheres to etched surfaces 17 and insures that panel 10 may be removed from the hardened concrete without destroying the desired decorative effect thereon. The etched panels can be used repeatedly without re-etching if care is taken to apply form oil to the etched surfaces before each use.

The term etching agent is herein used as referring to an acidic or basic agent which chemically removes the characteristic aluminum-oxide film from the surface of the aluminum panel, and reacts (typically with the evolution of hydrogen) with the stripped metal surface to dissolve and remove surface aluminum metal. The resulting etched and roughened surface has a tooth or irregular texture which is believed to provide improved adherence of the subsequently applied form oil. The tendency of the form oil to flow off the panel surface as wet concrete cascades into the form is thereby greatly reduced, and sticking of the panel to the resulting concrete structure is correspondingly alleviated.

The surface appearance of an adequately etched panel will vary depending on the alloying materials which are present in the aluminum. Most aluminum casting alloys form smut when treated with an acid or base etchant, and the development of a soot-colored or black surface indicates satisfactory surface roughening. If smut-forming materials are not present, an adequately roughened surface will normally have a frosted or satin appearance.

What is claimed is:

1. A method for forming a concrete structure in an as 4 sembly of aluminum panels having inner aluminum surfaces defining a construction for-m, comprising the steps of:

(a) applying an etching agent to the inner surfaces of the panels to roughen the inner surfaces; ('b) applying an oil substance to the surfaces treated with the etching agent; (c) pouring concrete into the construction form defined by the inner surfaces; ((1) allowing the concrete to harden into a formed structure; and (e) stripping the panels from the formed structure.

References Cited UNITED STATES PATENTS 1,575,122 3/1926 Madsen 1l75.3

2,669,752 2/1954 Pratt 264-337 2,806,277 9/1957 Hand et a1. 264-34 3,217,356 11/1965 Stutsman 26469 FOREIGN PATENTS 223,994 11/1924 Great Britain 264-415 766,858 l/ 1957 Great Britain 264338 ROBERT F. WHITE, Primary Examiner JEFFERY R. THURLOW, Assistant Examiner US. Cl. X.R. 

